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Geology of the Loughborough district — a brief explanation of the geological map Sheet 141 Loughborough

J N Carney, K Ambrose and A Brandon

Bibliographic reference: Carney J N, Ambrose, K and Brandon, A. 2002. Geology of the Loughborough district — a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Sheet 141 Loughborough (England and Wales).

Keyworth, Nottingham: British Geological Survey, 2003.

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Notes

The word 'district' refers to the area of the geological 1:50 000 Series Sheet 141 Loughborough. National grid references are given in square brackets and all lie within 100 km square SK. Borehole records referred to in the text are prefixed by the code of the National Grid 25 km2 area upon which the site falls, for example SK 21 NE.

Acknowledgements

We acknowledge those who provided data and who agreed to its transfer to the National Geological Records Centre, BGS Keyworth. We are especially grateful for the assistance provided by the Coal Authority and numerous civil engineering consultants. Landowners, tenants and quarry companies are thanked for permitting access to their land.

The grid, where it is used on figures, is the National Grid taken from Ordnance Survey mapping.

© Crown copyright reserved Ordnance Survey licence no. GD272191/2002.

Geology of the Loughborough district (summary - from rear cover)

The oldest rocks are late Precambrian in age and of volcanic arc origin. Exposed in the northern part of Charnwood Forest, they comprise the Charnian Supergroup together with thick intrusive diorite sheets. Mudrocks of the Swithland Formation probably represent part of the Cambrian-age Stockingford Shale Group and are unconformable on the Precambrian rocks.

Following Acadian deformation and subsequent erosion, Dinantian strata were laid down. They are largely concealed, but deep seismic investigations show that in the north they thicken to over 5000 m within the Widmerpool half-graben, an early Carboniferous extensional basin. The succeeding Namurian rocks include the Edale Shale Group, but only the overlying Millstone Grit Group occurs at the surface. Westphalian Coal Measures crop out in the south-west, in the North-west Leicestershire and South Derbyshire coalfields. Their mineral content of coal, ironstone and fireclay contributed to the early growth of the urban centres.

Permian rocks are thinly developed, but Triassic strata are of widespread outcrop. They comprise the Sherwood Sandstone Group overlain by the much thicker Mercia Mudstone Group with its characteristic red, clayey soils and with gypsum beds in its upper part. The Penarth Group, of dark grey mudstones and thin limestones, and the overlying mainly Jurassic-age Lias Group are the youngest bedrock components.

Unconsolidated Quaternary deposits form veneers on the higher ground, fill narrow channels carved into the bedrock, and occur on the wide floodplains of the district. The oldest of these deposits are referred to the Anglian glaciation of about 500 000 years ago. Amongst the youngest are the River terrace deposits and alluvium of the flood-prone Soar, Trent and Derwent valley floors. They constitute one of the major aquifers of the district and have been exploited for sand and gravel.

Current economic value comes from the 'hard rock', limestone, sand and gravel, coal, fireclay and gypsum resources of the district. Centuries of exploitation has resulted in large areas of artificially changed ground. However, it is clear that geoscience has an important and continuing role to play. It can assist in delineating despoiled or contaminated land, and in predicting the constraints that the rocks and superficial deposits of the district may pose to further development.

Chapter 1 Introduction

This Sheet Explanation provides a summary of the geology and applied geology of the district covered by the geological 1:50 000 Series Sheet 141 Loughborough published as a solid and drift edition in 2000. It is not intended to be a detailed field guide, but includes references to some of the key exposures of this geologically diverse district. A fuller description of the geology is provided by the Sheet Description (Carney et al., 2001), and detailed information can be found in the individual Technical Reports p.31.

The bedrock geology encompasses rocks that extend back over 600 million years (Ma) (Figure 1), (Figure 2). The oldest rocks crop out in Charnwood Forest, and belong to the late Precambrian volcanic and volcaniclastic sequence of the Charnian Supergroup. They are intruded by diorite sheets, which are also of Precambrian age. Unconformable upon the Precambrian rocks are Cambrian mudrocks of the Swithland Formation and Stockingford Shale Group, the latter proved only in a deep borehole. A major tectonic episode, the Acadian orogeny, was followed by erosion, and both are responsible for the unconformity that separates this 'basement' from the overlying Dinantian rocks. The Dinantian rocks crop out in rolling ground between Ticknall, Staunton Harold and Breedon on the Hill (Front cover). Elsewhere the Dinantian strata are wholly concealed, but there is much subsurface information to show that farther east they thicken to over 5000 m within the Widmerpool Half-graben, an early Carboniferous extensional basin bounded to the south and west by the Normanton Hills and Mackworth faults. The succeeding Namurian rocks include the concealed Edale Shale Group and, at outcrop, the overlying Millstone Grit Group. Sandstones and mudstones of the Millstone Grit form a scarp and dip-slope topography around Melbourne. The overlying Westphalian Coal Measures occur mainly in the North-west Leicestershire and South Derbyshire coalfields. Their mineral content of coal, ironstone and fireclay contributed to the early growth of the urban centres, and the various phases of mining activity have also profoundly affected much of the land surface on the 'Productive Measures' outcrop, though mineral extraction is today restricted to a few opencast workings. Faulting and block uplift during the end-Carboniferous Variscan orogeny was followed by some 50 to 60 million years of erosion. The only known Permian rocks are proved at depth, in the north-east of the area. Triassic rocks, by contrast, are widely distributed and comprise arenaceous strata of the Sherwood Sandstone Group overlain by the much thicker Mercia Mudstone Group. The latter gives rise to the red, clayey soils typical of much of this district and contains commercially significant gypsum beds in its upper part. The youngest rocks were deposited following a marine transgression. They are dark grey mudstones and thin limestones of the Penarth Group, and the overlying hard, grey, flaggy limestones and intercalated mudstones of the Barnstone Member, at the base of the Lias Group that is mainly of Jurassic age. These strata cap the steep-sided plateaux that dominate the landscape east of the River Soar.

Unconsolidated Quaternary deposits are patchily developed either as veneers to the higher ground or within narrow channels carved into the bedrock. The oldest, referred to the Anglian glaciation occurring about 500 000 years ago, comprise clay-rich till, glaciolacustrine deposits and glaciofluvial deposits of sand and gravel. The river terrace deposits and alluvium form the most continuous Quaternary tracts, and together constitute one of the major aquifers of the district. They underlie the flat pasture and wetland areas of the Soar, Trent and Derwent valley floors where thick deposits have been exploited for sand and gravel.

Chapter 2 Geological description

Precambrian

These rocks are seen in numerous craggy exposures within the hilly region of Charnwood Forest. They offer a rare insight into the cratonic 'basement' which otherwise deeply underlies the English Midlands. The Precambrian rocks are divisible into the bedded volcaniclastic sequence of the Charnian Supergroup, and late-stage intrusions, which in this district mainly consist of the North Charnwood Diorites. The lithostratigraphy for the Charnian Supergroup established by Moseley and Ford (1985), and modified by Carney (1994) is followed herein (Figure 3), but note is also taken of the revisions suggested by McIlroy et al. (1998), who maintained that the uppermost unit, the Brand Group, is probably of Cambrian age.

Charnian Supergroup rocks have an aggregate thickness of at least 3800 m, with no base proved. Their distribution is controlled by a south-east-plunging anticline, which brings the lowermost units progressively to crop in the north-west. All of these rocks are cleaved and recrystallised at epizonal (greenschist-facies) metamorphic grades, but sufficient textural and mineralogical details have survived to show that this supergroup is mainly volcanic in origin. Chemical studies of the igneous lithologies suggest that the Charnian magmas were calc-alkaline in composition, comparable to the magmas of modern volcanic arc systems of the type that are founded upon oceanic or attenuated continental crust (Pharaoh et al., 1987). The predominance in the Charnian of well-stratified volcaniclastic lithologies (terminology of Fisher and Schmincke, 1984), and the presence ofEdiacara-type fossil assemblages, together indicate deposition in sea marginal to a vol-anic arc. The commonest sedimentary structures include normal grading (Plate 1) and slumped bedding and reflect the supply of volcanic material either directly, by subaqueous pyroclastic flows, or by the secondary reworking of previously deposited material within debris flows and turbidity currents that travelled some distance into the depositional basin. In the north-west of Charnwood Forest there are massive andesitic and dacitic lithologies, in the Whitwick Volcanic Complex, which have a more primary volcanic origin. Their occurrence in close proximity to very coarse, volcanic breccias of the Charnian Supergroup suggests associations of rocks that formed around active volcanic centres (Carney, 1999). The principal style of eruption involved the uprise of extrusive domes which subsequently collapsed, giving rise to debris flows and pyroclastic block flows now seen as breccias (Carney, 2000).

A latest Precambrian (Neoproterozoic III) age for the Charnian volcanism is indicated by the Ediacaran fossils which are found throughout the sequence between this and of dark greenish grey to black, flow-banded, porphyritic dacite and subordinate intercalated fine-grained tuffs. The Ives Head Formation (IvH) is well exposed at Morley Quarry. It is a sequence of pale to medium grey, bedded to laminated, volcaniclastic mudstones and siltstones interspersed with thicker and more massive, crystal and lithic-rich tuffaceous sandstones (saV) grading to matrix-supported breccia (brV), the latter commonly with abundant material of pyroclastic derivation. In the type area around Ives Head summit, the top surface of a typical graded bed (Plate 1) contains impressions of ?medusoid Ediacaran fossils of the genus Ivesheadia, Shepshedia and Blackbrookia. The formation is capped by the South Quarry Breccia Member (SQB), about 30 m thick where seen at One Barrow Plantation [SK 4639 1714]. Here a distinctive bed shows evidence for intraformational slumping, with folded sedimentary rafts, up to 1.5 m long, in a matrix of coarse, crystal-rich, volcaniclastic sandstone. The Blackbrook Reservoir Formation (Blk) consists of greenish grey, volcaniclastic mudstones, siltstones and subordinate sandstones in the the adjacent Coalville district (Boynton and Ford, 1995, 1996). However, controversy has surrounded the precise age of this magmatism. One suggestion that it occurred prior to 603 Ma is based on correlations with the Precambrian rocks of Nuneaton, which are intruded by a diorite dated radiometrically by the U–Pb method (Tucker and Pharaoh, 1991). On the other hand, a much younger value of 580 Ma is currently favoured for the base of the fossil-bearing Ediacarian subdivision of the Neoproterozoic. The age of the uppermost Charnian unit, the Brand Group, is now likely to be Lower Cambrian since the trace fossil Teichichnus has recently been found in strata of the Swithland Formation, to the south of this district (Bland and Goldring, 1995).

The Blackbrook Group commences with the oldest recognised Charnian unit, the Morley Lane Volcanic Formation (MLV), proved only in the Morley Quarry No. 1 Borehole [SK 4765 1787]. It is composed mainly type section at Blackbrook Quarry [SK 4563 1797]. Farther east at Newhurst Quarry [SK 4898 1786] individual beds, up to 2 m thick, have sharp bases and show multiple grading. Other lithologies include multistorey volcaniclastic sandstones (saV) in sequences up to 5 m thick, and massive, matrix-supported breccia with both sedimentary and volcanic clasts (brV).

The Maplewell Group contains the main pyroclastic component of the Charnian Supergroup. In the eastern outcrops this is a well-bedded sequence but it passes westwards into the Charnwood Lodge Volcanic Formation, dominated by volcanic breccias occurring in close spatial association with the Whitwick Volcanic Complex. The Beacon Hill Formation commences with the Benscliffe Breccia Member (Ben), about 20 m thick where seen at Roe's Plantation [SK 4968 1635] but thickening to 100 m in the west. This is a massive to thickly bedded, pyroclastic rock with a crystal-rich matrix enclosing lapilli and small blocks of microcrystalline andesite or dacite. The Beacon Tuff Member (BcT), about 875 m thick, consists of blue-grey, hard ('flinty'), laminated and graded, tuffaceous mudstones and siltstones near Nanpantan [SK 4995 1687]. There are intercalations up to 180 m thick of massive, dacitic, lithic-crystal tuff (ZD) locally grading to volcanic breccia [SK 5017 1618]. The Sandhills Lodge Member (ShL) comprises about 20 m of pale grey, coarse-grained, crystal-rich tuffaceous sandstone enclosing fine-grained sedimentary rafts showing plastic deformation; vitric (y-shaped) shards are common to both matrix and volcanic clasts. The Buck Hills Member (BHM) is about 800 m thick and is well exposed at the type area around Buck Hill ridge [SK 5071 1676]. It is composed of blue-grey, parallel-laminated and graded, volcaniclastic mudstones, siltstones and sandstones with vitric tuff laminae and beds of massive to graded sandstone (saV) up to a few metres thick. The Outwoods Breccia Member (OtB) is about 120 m thick in the type area of the Out Woods [SK 5138 1666]. It contains numerous breccia beds, from 1 to 7 m thick, with abundant contorted sedimentary clasts in a crystal-rich sandstone matrix. The overlying Bradgate Formation (BT), where seen close by [SK 5149 1656], comprises predominantly grey, fine-grained, parallel-laminated, vitric tuffs. In the western outcrops there are thick graded sequences of tuffaceous sandstone fining upward to siltstone or mudstone cappings.

In the western outcrops, the Charnwood Lodge Volcanic Formation (CLV) includes in its undivided part massive to thickly bedded, andesitic volcanic breccia (the 'bomb rocks' of Watts, 1947) and parallel-stratified lithic-lapilli or lithic-crystal tuff. The St. Bernard Tuff Member (SBT), about 100 m thick around Saint Bernard Abbey [SK 4582 1621], consists of massive lithic-crystal tuff passing up into volcanic breccia and then to a capping of thinly bedded and graded crystal tuff. The Swannymote Breccia Member (SB) is about crystal-rich matrix that is locally intermixed with siltstone. The Cademan Volcanic Breccia Member (CVB) comprises up to 450 m of volcanic breccia that is typically unbedded around Calvary Rock [SK 4338 1717]. The included blocks are angular to subrounded (Plate 2), locally in excess of 1 m across, and of a uniform, fine-grained, high-silica andesite that is both lithologically and chemically identical to the Grimley Andesite (see below).

The Whitwick Volcanic Complex encompasses the massive or autobrecciated lithologies that crop out discontinuously within the Charnwood Lodge Volcanic Formation and thus may be genetically related to it. The Peldar Dacite Breccia (PDB) is up to 520 m thick around Whitwick Quarry, and blocks of it can be seen in the wall of Saint Bernard Abbey. It is a type of hyaloclastite breccia containing numerous rounded to elliptical fragments of black to dark grey, porphyritic (plagioclase-quartz) dacite in a medium-grained crystal-rich, spher-ulitic volcaniclastic matrix. The Sharpley Porphyritic Dacite (SyP) is up to 600 m thick around the type area of High Sharpley [SK 4485 1707]. It has a phenocryst assemblage similar to that of the Peldar Dacite Breccia but is a more homogeneous, pale grey to lavender lithology, identical to the blocks in the Swannymote Breccia. The Grimley Andesite (GyA), up to 900 m thick, is spatially associated with Cademan Volcanic Breccia; it is a green to greyish green, moderately plagioclase-phyric, high-silica andesite or dacite which locally is intensely autobrecciated, as seen in crags around Whitwick [SK 4370 1637].

Intrusions of the North Charnwood Diorites (HD) form near-vertical to inclined andesitic sheets, up to 60 m wide and generally with north-westerly and easterly orientations. In the small quarries near Buck Hill [SK 5064 1649] they are grey rocks with a coarsely mottled texture due to the enclosure of white, subhedral plagioclase crystals within a granular, quartzo-feldspathic mesostasis containing several per cent of granophyric intergrowths. A second intrusive type, the Lubcloud Microgranite (FG), occurs as a north-west-trending dyke, about 9 m wide. exposed south of Ives Head summit. It has a red, saccharoidal, quartzo-feldspathic matrix enclosing plagioclase phenocrysts.

Cambrian

The only Cambrian strata at outcrop in this district occur in the east of Charnwood Forest and are assigned to the Swithland Formation (SG), representing the uppermost unit of the Brand Group (Moseley and Ford, 1985). In a roadside exposure near Nanpantan [SK 5103 1739] they comprise purple or maroon, volcaniclastic siltstones and coarse-grained to pebbly, crystal-rich sandstones with siltstone intraclasts.

Over 39 m of the Stockingford Shale Group (SSh) was proved in the Ticknall Borehole [SK 4203 1694] between the Calke Abbey Sandstone and terminal depth at 209.04 m. Allowing for the steep dip, this represents a minimum stratal thickness of 25 m. Black to dark grey and pale grey, pyritous, laminated mudstones and silty mudstones are dominant, and are weathered to green and red for 11 m beneath the Calke Abbey Sandstone. The Middle or early Upper Cambrian age for these beds is based on a fragmentary fauna including the trilobite Agnostus pisiformis (Rushton, 1995) and sparse acritarchs (Molyneux, 1995), and invites correlation with the type marine Cambrian sequence at Nuneaton, in the Coventry district. The near-vertical, penetrative cleavage seen in the borehole core is attributed to Acadian (Siluro-Devonian) regional compression.

Dinantian

Dinantian rocks crop out as inliers between Ticknall, Breedon on the Hill (Front cover) and Grace Dieu, and elsewhere are proved at depth. They were deposited within a block- and-graben province that developed in response to early Carboniferous crustal extension across the region. The resultant structural configuration (see inset on Sheet 141 Loughborough) explains the considerable thickening of the concealed Dinantian strata to the north-east of the Normanton Hills and Mackworth faults, where they form a basinal sequence within the Widmerpool Half-graben (Ebdon et al., 1990). By contrast, the exposed part of the Dinantian was deposited in shallower waters on the Hathern Shelf, delineated by the Thringstone, Burton and Sileby faults. These shelf sequences are considerably attenuated in thickness, relative to the contemporary strata in the Widmerpool Half-graben.

The Hathern Anhydrite Formation (HaA) is probably of Courceyan age and is the oldest unit proved in the Hathern No. 1 Hydrocarbon Borehole [SK 5158 2416]. It consists of cyclically bedded anhydrite, carbonate rocks and mudstone and represents a restricted basin, sabkha-type association deposited on the Hathern Shelf.

The Milldale Limestone Formation (Mi) of early Chadian age consists of well-bedded dolostones (Plate 3) with partings of green and grey, commonly bituminous clay, mudstone and siltstone. In Cloud Hill Quarry, rare undolomitised sections show crinoid and shell-rich, bioclastic and ooidal grainstones, and locally there are sandy beds with pebbles indicative of shallow-water, storm-dominated depositional settings on the Hathern Shelf. Foraminifera diagnostic for age dating have been found in chert nodules, and the quarry is the type locality in Europe for the large brachiopod Levitusia humerosus. The succession around Breedon on the Hill was deposited in deeper waters, as indicated by the quarry exposures showing an intercalation of about 100 m of predominantly unbedded dolostone of mud-mound (Waulsortian) reef facies (mmr); fossils in the latter include the early Chadian ammonoid, Fascipericyclus fasiculatus. The formation attains at least 400 m thickness in the Breedon on the Hill area, but is absent 4 km to the west and was not encountered in the Ticknall Borehole.

The Calke Abbey Sandstone Formation (CAS) does not crop out but was encountered in the Ticknall Borehole. The formation overlies unconformably the Stockingford Shale Group and consists of brown to green-grey, pebbly, feldspathic sandstones and conglomerates, which represent a fluviatile association and contain possible Charnian volcanic clasts. They are intercalated with 'overbank' beds of green mudstone, siltstone and sandstone, commonly showing vermicular rootlet mottles and desiccation cracks indicative of periodic emergence and pedogenic modification. The formation is undated but the overlying units suggest it must be older than Asbian.

The Arch Farm Sandstone Formation (ARFS) comprises 9 m of strata overlying the Calke Abbey Sandstone in the Ticknall Borehole. Its base is interpreted as a major marine flooding surface, and its top is probably disconformable below the Cloud Hill Dolostone. The formation, which is undated, was deposited in a near-shore marine setting and consists mainly of green to grey, fine- to medium-grained, laminated or cross-laminated sandstones with pebble-rich lenticles and shelly lags containing fragments of Lingula. The upper part shows pedogenic features, such as listric surfaces and sporadic small ferruginous concretions. The Cloud Hill Dolostone Formation (CHD) is late Holkerian to early Asbian and possibly Brigantian in age. At the type section in Cloud Hill Quarry, it is at least 125 m thick and is seen to rest with sharp, angular unconformity upon flexured and locally vertical beds of the Milldale Limestone. This unconformity is called the 'Main Breedon Discontinuity' and represents a time-gap of 7 to 10 Ma. In the north of the quarry, the lower part of the formation consists of red and grey, laminated mudstones and dolomitic siltstones. These are overlain by a mud-mound reef facies (mmr) of dolostone, also seen at Barrow Hill Quarry [SK 421 201], containing fossils of the late Asbian or Brigantian ammonoid Goniatites. The basal mudstone-rich sequence shows intense deformation, (Plate 4), thrusting and asymmetric folding which is thought to reflect east-directed, intraformational slumping of packages of largely lithified beds. At Breedon Hill Quarry, a reddened bedding plane crowded with the trace fossil Thallasinoides is taken as the unconformity surface on the Milldale Limestone.

The Ticknall Limestone Formation (TL), of mainly Brigantian age, forms the extensive Dinantian outcrops around Ticknall [SK 3626 2370] and Calke, and the smaller inliers at Grace Dieu and Osgathorpe. In the Ticknall Borehole, it unconformably overlies the Cloud Hill Dolostone. The formation consists of shallow water to semi-emergent facies associations of bedded fossiliferous dolostones with karstic layers and palaeosols, but locally contains dark grey mudstones with debris of the large brachiopod Gigantoproductus.

The Long Eaton Formation (LE) ranges from early Chadian to late Asbian in age but contains a major unconformity, similar to the one at the base of the Cloud Hill Dolostone, with late Chadian to Arundian strata missing. It represents a basinal facies association that is confined to the Widmerpool Half-graben where it forms a major part of the concealed Dinantian syn-rifting sequence. At least 1867 m of this formation were proved to terminal depth in the Long Eaton No. 1 Borehole [SK 4640 3166], but seismic interpretations such as the depth section portrayed on Sheet 141 Loughborough show it attaining close to 4000 m in the immediate hanging wall of the Normanton Hills Fault. Borehole samples indicate a succession of graded calcareous mudstones, siltstones, and clastic limestones. The succeeding Lockington Limestone Formation (Loc), of late Asbian or early Brigantian age, consists of 15 to 30 m-thick packages of brown, argillaceous to sandy, turbidite limestones separated by thinner sequences of pyritic, carbonaceous mudstone.

The Widmerpool Formation (WdF) is mainly Brigantian in age. It is not exposed but a complete section of 741 m total thickness is known from the Ratcliffe on Soar Borehole [SK 5081 2913]. The few core samples are mainly of dark to pale brown, calcareous and locally carbonaceous, pyritic mudstones grading to argillaceous limestone or calcareous sandstone. Near the top the Ratcliffe Volcanic Member (RAVO) comprises five thin tuff beds within about 124 m of green or brown mudstone. It is correlated with tuffs within the P2 Zone in the Duffield Borehole of the Derby district. Attenuated equivalents of the Widmerpool Formation were deposited on parts of the adjacent Hathern Shelf. These include 130 m of mudstones and argillaceous limestones in the Ashby No. G1 Borehole [SK 3134 2524].

Namurian

Namurian rocks were deposited early during a post-rifting phase of thermal subsidence across this region. Their oldest representatives are mudrocks, correlated with the Edale Shale Group, which partially filled the remaining tectonic basins. The overlying Millstone Grit Group contains thick sandstones deposited within shallow water deltas that prograded into the district from the north and east (Fulton and Williams, 1988). Variations in sea level within the Namurian are reflected by cycles of sedimentation that commonly commence with the deposition of marine mudstones, including fossiliferous beds. These marine bands can be correlated across large areas and each is generally recognised by the presence of a diagnostic ammonoid (goniatite) fauna. Various marine bands define the boundaries of seven stages into which the Namurian Epoch is divided (Figure 1).

The Edale Shale Group (ESh) attains a minimum proven thickness of 166 m below Triassic strata in the Ratcliffe on Soar Borehole; sampled intervals indicate sequences of dark grey mudstones, thin turbiditic siltstones and subordinate sandstones. Wireline log correlations with the Duffield Borehole, located within the Widmerpool Half-graben some 40 km to the north-west, suggest that these strata are of Pendleian age, ranging from the E1a1 (Cravenoceras leion) Biozone at the base, to the E1c1 (Cravenoceras malhamense) Biozone. On the Hathern Shelf, the group's occurrence is suggested by Arnsbergian-age mudstones with Eumorphoceras ferrimontanum (E2a2) in the Ashby G1 Borehole.

The Millstone Grit Group (MG) has its main outcrop around Melbourne, and forms smaller inliers elsewhere. Its age is constrained by the faunal assemblages of the marine bands and ranges from the mid-Arnsbergian to Yeadonian stages. The group is mainly distinguished from the Edale Shale by the abundance of its sandstones. These locally form aquifers and details of their thicknesses are given in (Figure 1). The sandstones are commonly multistorey, cross-bedded, coarse grained and highly feldspathic, and their tops may be capped by fossil soil horizons (seatearths), with coal seams rarely developed, representing periods when the landsurface was covered by vegetation. They form the upper parts of cyclic sequences (cyclothems), which commence with marine mudstones and coarsen upwards through siltstones. Cross-bedding measurements on individual sandstone beds indicate deposition by river systems flowing towards the west or north-west. In this district the Millstone Grit succession is attenuated, compared with the thickness of equivalent strata farther north in the Pennine Basin. It thins markedly from about 160 m around Melbourne to 115 m farther south, in the Worthington Borehole, where the base of the group is unconformable on the Ticknall Limestone Formation. There are further non-sequences higher in this borehole where rocks of the Yeadonian and part of the Marsdenian stages are missing below the Lower Coal Measures.

Westphalian rocks

The main Westphalian outcrop is limited to the south-west of the Thringstone Fault, with scattered small outliers near Melbourne. The strata thin southwards, as well as eastwards across the Boothorpe Fault and Ashby Anticline (Figure 10). Those structures in combination define the boundary between the North-west Leicestershire Coalfield, in the east, and the South Derbyshire Coalfield to the west. Westphalian sedimentation accompanied progressive regional subsidence, and at times the district was subjected to flooded, swampy conditions in which organic material accumulated to form the coal seams.

The Coal Measures represent cyclic sedimentary sequences deposited mainly in upper delta plain environments. Typically these commence in dark grey mudstones, with mussel bands or marine bands respectively denoting lacustrine or marine environments. These are succeeded by mudstones interbedded with laminated and micaceous siltstones (overbank/lacustrine delta) which in turn pass up to medium-grained, grey feldspathic sandstones of proximal delta or channel facies. Pale grey, ganisteroid sandstones or mudstones represent the seatearths of some coal seams (peat mires). The base of the Coal Measures is taken as the base of the Subcrenatum (Pot Clay) Marine Band (SBMB), and other marine bands are used for convenience to divide the measures into three groupings. Details of seams in the Coal Measures, and the extent of their workings, are given in (Figure 4) and (Figure 5). The Lower Coal Measures (LCM), of Langsettian (Westphalian A) age, includes the strata between the bases of the Subcrenatum and Vanderbeckei (VDMB) marine bands. It ranges in thickness from 330 m in the North-west Leicestershire Coalfield to about 420 m in the South Derbyshire Coalfield. The Kilburn (K) seam marks the base of the 'Productive Measures', and its outcrop thus delimits the extent of undermined ground. Notable sandstones include the Wingfield Flags (WF), locally up to 65 m thick, and sandstones above the Eureka (E) Coal (the 'Eureka Rock') and below the Vanderbeckei Marine Band. In the former Lounge opencast site [SK 385 185] in the Leicestershire Coalfield the Nether Lount (NL) and Middle Lount (ML) seams are locally washed out by narrow sandstone-filled channels oriented east-south-east, this being also the direction of current flow within the channels (Jones, 1994). The coal seams are generally between 0.5 and 2 m thick although the components of the Main Coal of the South Derbyshire Coalfield locally unite to form a single seam up to 5.5 m thick. The Middle Coal Measures (MCM), of Duckmantian to Bolsovian (Westphalian B and C) age, lie between the base of the Vanderbeckei Marine Band and the top of the Cambriense (Top) Marine Band (CMB). Here, coal seams are generally between 1 and 2 m thick throughout the district. In the South Derbyshire Coalfield these measures have an aggregate thickness of 360 to 400 m and include the boundary between the Duckmantian and Bolsovian, which is taken at the base of the Aegiranum Marine Band (AMB). The P40 Coal forms the base of the commercially important 'Pottery Clays Formation' (Plate 5). In this higher part of the Middle Coal Measures, coals are more numerous, their vertical separation decreases, and there are several marine bands. In this condensed sequence, the seatearths are unusually thick, up to 4 m (Figure 4), and constitute a fireclay resource. The Pottery Clays extend upwards to include the whole of the Upper Coal Measures (UCM), whose base at the top of the Cambriense Marine Band lies just above the P17 Coal.

The succeeding Warwickshire Group constitutes a 'red bed' association, deposited when local uplift initiated a change from swampy environments to better-drained conditions. The single proving in this district is in the Caldwell No. 2 Borehole [SK 2568 1672], where 44.7 m of mainly reddish brown mudstones with purple, yellow, green and blue-grey mottles is correlated with the Etruria Formation (Et).

Permian

Permian strata occur at depth in the north-eastern corner of the district, where the Central Ordnance Borehole [SK 5059 3501] proved 14.3 m of red mudstone, assigned to the Edlington Formation (EdF).

Triassic

Triassic strata variously occur at rockhead or at depth over approximately 80 per cent of the district. In latest Permian and earliest Triassic times (about 250 Ma) mainly continental-facies deposits began to accumulate across an eroded landscape, eventually burying rugged palaeo-hill ranges developed on the Pre-cambrian outcrops of Charnwood Forest and the steeply dipping Dinantian strata around Breedon on the Hill. A thick Triassic sequence filled the Needwood Basin, which was an area of active subsidence along and to the west of the Coton Park and Burton faults (Figure 10).

The Moira Formation (Mo) is a variably developed unit, in part bounded by unconformities, with a maximum of 52.4 m recorded in the Coton Park Colliery Borehole [SK 2732 1792]. It comprises beds of breccia, sandstone and mudstone, the former bearing clasts derived mainly from local Carboniferous, Lower Palaeozoic and Charnian terrains. A finer grained, fluviolacustrine facies, locally exposed around Ingleby [SK 349 279] and near Ticknall [SK 3576 2424], comprises red-brown or green micaceous mudstones interbedded with red to buff, fine- to medium-grained sandstones.

The Sherwood Sandstone Group rests unconformably on pre-Triassic rocks and, locally, the Moira Formation. The earliest strata, proved only in the Chilwell Borehole [SK 5059 3431], consist of red sandstones and mudstones of the Lenton Sandstone Formation (LnS), of Permian to Triassic age. The Polesworth Formation (Figure 6), formerly the 'Bunter Sandstone' or 'Pebble Beds', crops out only in the western half of the district and consists largely of crossbedded, medium- to coarse-grained, pebbly sandstones. The north-westerly to northeasterly current directions, measured from cross-bedding, show that the strata were deposited from rivers draining into the district from the south. Westward thickening of this formation to over 150 m near Caldwell, reflects contemporaneous subsidence within the Needwood Basin (Figure 10). In the north-east of the district the Polesworth Formation is thought to pass at depth into the Nottingham Castle Sandstone Formation of the Nottingham district. The Bromsgrove Sandstone Formation (BmS) (Figure 6), formerly the 'Lower Keuper Sandstone', onlaps the Polesworth Formation and represents widespread alluviation across lower lying parts of the district in early to mid-Triassic times; measurements of cross-bedding structures indicate deposition from river systems flowing to the north-west, north-east and south-east. The strata are well exposed in quarries near Castle Donington [SK 4176 2756]. The unit is generally 30 to 50 m thick, but up to 110 m of strata accumulated to the southwest of the Coton Park Fault, within the Needwood Basin. The Shepshed Sandstone Member (ShS) is confined to the area within and around Charnwood Forest, where it is possibly up to 50 m thick in palaeovalleys. Its beds are commonly massive, but with parallel stratification locally emphasised by concentrations of angular to subangular Charnian clasts.

The Mercia Mudstone Group (Figure 6) records the progressive waning of fluvial deposition in its lowermost two formations, to be replaced by arid continental sedimentation involving aeolian processes and ephemeral lacustrine or sheetflood deposition. The lower formations thicken westwards across the Burton Fault, into the Needwood Basin. The group as a whole is poorly exposed, but in boreholes its components can be identified on the basis of their geophysical log signatures (Figure 6), which in turn are controlled by progressive changes in clay mineralogy. The group commences with the Sneinton Formation (Figure 6), formerly the 'Waterstones', succeeded by the Radcliffe Formation, the latter representing a lacustrine facies association. The Gunthorpe Formation (Figure 6) contains numerous thin beds of greenish grey, dolomitic siltstone and very fine-grained sandstone, the 'skerries' of former terminology; they include the Diseworth Member, up to 5 m thick. The Breedon Member (Br), patchily developed, but up to 5 m thick around Breedon on the Hill and Barrow Hill, contains angular to subangular clasts of partially rotted Dinantian dolostone in a matrix of dark red-brown, very clayey, fine-grained, sandstone. The Edwalton Formation, (Figure 6) is similar to the Gunthorpe Formation and its field recognition usually depends on identifying two relatively thick sandstones. At the base is the Cotgrave Sandstone Member consisting of fine- to medium-grained, parallel-laminated sandstone interbedded with red mudstone. The topmost unit is the Hollygate Sandstone Member, up to 11 m thick, consisting of interbedded grey-green and red-brown, fineto coarse-grained sandstones with subordinate structureless siltstones and mudstones. The overlying Cropwell Bishop Formation (Figure 6), contains the thicker gypsum beds that have been mined underground; the most important are the Tutbury Gypsum (T), ranging up to 5 m thick, and the Newark Gypsum (N) featuring several thin gypsum seams within about 10 m of beds. A sharp colour change marks the boundary with the overlying Blue Anchor Formation (Figure 6), formerly the 'Tea-green Marl', of Norian to Rhaetian age, reflecting a transition from continental to marginal marine environments.

The Penarth Group was laid down during a major (Rhaetian) marine transgression. The two component formations were formerly well exposed in the Normanton Hills railway cutting [SK 5382 2474]. At the base is the Westbury Formation (Wby), comprising about 4 m of dark grey to black, fissile, pyritous mudstones with a few thin beds of siltstone and sandstone and containing bivalves; the 'Rhaetic Bone Bed' is locally present just above the base. The succeeding Lilstock Formation, of which only Cotham Member (Ctm) is mappable, is a pale grey to greenish grey, calcareous mudstone with small limestone nodules and a thin basal limestone. The overlying Langport Member, 0.25 m thick, is represented by a hard, pale grey micrite recognised only in the Normanton Hills railway cutting.

Jurassic

Jurassic strata occupy narrow plateaux to the east of the Soar Valley. Only the lowest part of the Lias Group (the Scunthorpe Mudstone Formation) is represented, by the Barnstone Member (Bst), formerly the 'Hydraulic Limestones'. This member was deposited in shallow marine environments; it consists of blue-grey mudstones with several intercalated layers of hard, thinly bedded micrite or shelly limestone. The base of the Hettangian stage, and hence of the Lower Jurassic, is taken at the earliest appearance of ammonites of the genus Psiloceras, about 3 m above the base of the member.

Quaternary

The Quaternary Period, covering about the last 2 million years, was marked in Britain by extreme oscillations of climate ranging from cold glacial or periglacial to mildly temperate conditions. These oscillations are reflected in the scheme of marine oxygen isotope (o.i.) stages to which the deposits are tentatively referred on (Figure 7). The oldest Quaternary sediments, mainly tills, were deposited by continental ice sheets which advanced across the district during the Anglian cold stage (o.i. stage 12); a useful basis for naming these tills was provided by Rice (1968). Glaciofluvial outwash during the waning phases of the Anglian glaciation initiated the present-day drainage systems. Early deposits, including the valley sandar and later fluvial sediments, the river terrace deposits of the trunk valleys, record climate change coupled with continuing uplift and lateral and vertical incision. Terrace thalwegs for this district indicate about 7 m of incision between each successive cold stage aggradation. Towards the end of the Late Devensian stage (o.i. stage 2), an Irish Sea ice sheet advanced westwards into the Trent and Dove catchments around Uttoxeter and fed considerable outwash downstream through this district. Flandrian (o.i. stage 1) events are marked by fluvial incision and terracing of the outwash and coeval sediments along the trunk valleys, and by the influence of human activities on the landscape.

The Anglian glaciation formed the wide variety of glacial deposits summarised in (Figure 8). A trans-Pennine lobe of the ice sheet advanced from the north-west and deposited the Thrussington Till (Figure 8). From the east and north-east, a second ice lobe encroached slightly later, depositing the Oadby Till (Figure 8) mainly of eastern derivation but locally with a red, Triassic-rich variant. South of this district, till has been recorded at 230 m above OD on Bardon Hill in Charnwood Forest indicating that the ice completely overrode this hilly area. Occurrences of glaciofluvial deposits comprise the sands and gravels carried by meltwater systems draining from or beneath the ice sheets, whereas the less common glaciolacustrine deposits consist of brown, laminated silts and clays laid down within ice-ponded lakes.

Four sediment-filled channels, or tunnel valleys, carved by pressurised subglacial water into the underlying bedrock, have been mapped; they trend roughly parallel to the present-day Trent valley (Figure 9). They are known to cut down to below 25 m above OD, and to have infills dominated by glaciolacustrine deposits, of which the Findern Clay is a representative.

River terrace deposits were formed under a wide range of conditions (Figure 7), but generally mark periods when deposition outweighed erosion in the major valleys. The river terrace nomenclature adopted here, in part, follows the schemes of Clayton (1953) and Posnansky (1960) and, in part, the correlations of Trent terraces in Lincolnshire by Brandon and Sumbler (1988, 1991). The terrace deposits are of variable thickness (Figure 8). Their stone clasts derive from reworking of the older drift deposits and bedrock, and the proportions of the main constituents vary between the valleys, although 'Bunter pebbles' and shattered flints are always prevalent. Interglacial deposits with age diagnostic fossils, for example the Crown Inn Beds (Figure 7), are confined to channels cut in bedrock and are rarely exposed. Remnants of a rubified temperate palaeosol, the Hykeham Soil, of probable Ipswichian age, (o.i. stage 5e) occur in the upper part of the Etwall and Egginton Common terrace deposits of the Trent valley. Periglacial processes, involving solifluction, occurred in areas not covered by ice during or at the end of the glacial periods. These processes helped to promote the formation of head. In Charnwood Forest, head forms a widespread veneer of sandy silt with numerous Charnian blocks.

Flandrian (or Recent) deposits comprise the Hemington Terrace Deposits, consisting of gravels capped by clays and silts, which overlies bedrock, or Holme Pierrepont Sand and Gravel. The present-day floodplain lies 0.5 to 1 m below the Hemington Terrace Deposits and forms the water meadows and meander belts of the rivers. The underlying alluvium of the main trunk streams comprises up to 5 m of gravel overlain by up to 2 m of mottled grey and brown overbank clayey silts; it is generally thinner and more clay-rich in smaller tributaries. Lacustrine deposits (Figure 8) floor shallow bedrock depressions, the largest of which are the Sinfin and Gotham 'moors'. Such areas are commonly ascribed to dissolution-induced subsidence above the gypsiferous Cropwell Bishop Formation. Though wide in aerial extent, these deposits are generally thin (Figure 8). Older lacustrine deposits, shown on the published map by the superscript '1', are of similar type but form flat-topped terrace features 1 to 3 m higher than the surrounding lacustrine deposits.

Landslips in the district are recorded mainly on slopes in excess of 20º and with a cover of till or deeply weathered mudstone. Made ground represents areas where human activities have caused material to be deposited on the natural ground surface. It is most extensive, if not ubiquitous, in the main urban centres where it is not shown on Sheet 141 Loughborough. In some other areas, where the topographical features associated with made ground, especially colliery or quarry infill spoil, were landscaped prior to redevelopment, the extent of made ground is based largely on site investigation data. Infilled ground comprises areas where excavations have been partly or wholly backfilled. Workings for sand and gravel, coal, fireclay and brick clay and disused railway cuttings are the principal repositories for the disposal of waste materials. They may include excavation and overburden waste, construction and demolition materials, domestic refuse and industrial waste. Where excavations have been restored, no surface indication of the original void may remain and their delineation relies on archival sources.

Worked ground represents those areas where material has been removed, for example in open quarries and pits, road and railway cuttings and general landscaping. Disturbed ground is not shown on Sheet 141, but has been mapped in detail on the constituent 1:10 000 scale geological maps.

In the coalfields it includes ground that has commonly experienced the effects of more than a single phase of mineral extraction, involving combinations of surface, shallow subsurface (bell-pits, pillar and stall workings) and deep underground mining techniques. In the outcrop of the Cropwell Bishop Formation, former surface and subsurface workings for gypsum have also caused disturbed ground. Landscaped ground, shown only on the 1:10 000 scale maps, comprises areas, typically of urban or industrial development, where the original surface has been extensively remodelled, but where it is impractical or impossible to delineate areas of cut or made ground.

Structure, metamorphism and concealed geology

The main structures (Figure 10) reflect the location of the district at a boundary between two major basement provinces (Lee at al., 1990), the Midlands Microcraton and Eastern Caledonides. This junction is thought to be a wide, complex zone in part defined by the Thringstone Fault. Surface faults and folds in the district have north-westerly orientations, and are related to the structural grain of the 'Eastern Caledonide' basement. Subsidiary faults trending east to north-east are also attributed to a Caledonide inheritance. Northerly 'Malvernian' basement trends, characteristic of Midlands Microcraton crust, are found mainly in the extreme west of the district.

The features portrayed on the two geophysical map-insets of Sheet 141 Loughborough reflect the influence of the 'basement' on large shallow structures. The Bouguer gravity inset shows a pronounced north-west elongated anomaly 'high', indicative of relatively dense uplifted basement. The margins of this ridge are in part delimited by the Thringstone Fault and (concealed) Breedon Fault on its north-eastern side, and by the Boothorpe Fault to the south-west. Weaker gravity features coincide with the Normanton Hills and Sileby faults. The aeromagnetic anomaly inset shows a 'high', over the central to eastern part of this district, which is comparable to other anomalies in the East Midlands produced by late Ordovician granodiorite intrusions that have either been proved in boreholes or, as near to Mountsorrel, found at outcrop. The results of geophysical modelling of the 'Diseworth Intrusion' are incorporated in the depth section at the foot of Sheet 141 Loughborough; its northern margin has constrained the location of the Normanton Hills Fault and hence, the south-western margin of the Widmerpool Half-graben.

Pre-Carboniferous deformation folded the Charnian Supergroup and Brand Group into a south-east-plunging anticline (Figure 3), at the same time imposing epizonal (greenschist facies) metamorphism and a pervasive, west-north-westerly cleavage which cuts across (transects) the anticlinal axis. The Charnian cleavage fabric was almost certainly imposed at the same time as that affecting Cambrian strata in the Ticknall Borehole, and is dated as Acadian (Siluro-Devonian) age. This deformation was closely followed by north-easterly to northerly cross-faulting exemplified by the Abbot's Oak Fault (Figure 3), with a dextral throw of about 1300 m.

The Dinantian deformation was characterised by regional crustal extension, the effects of which are mainly evident to the north and east of the Sileby–Thringstone fault systems. Maximum subsidence, totalling at least 5500 m, occurred along the Mackworth and Normanton Hills faults, which define the margin of the Widmerpool Half-graben (or 'Gulf'). That structure is flanked on its footwall (south-western) side by the Hathern Shelf, a tilted block on which an attenuated Dinantian succession was deposited. In Cloud Hill Quarry, complex fold and thrust deformation affects the Hathern Shelf sequence (Plate 4). It may reflect large-scale slumping and/or detachment faulting during one of the major syn-Dinantian rift or rift-inversion episodes affecting the region. Namurian to Westphalian deformation, which characterised the post-rift tectonic environment, involved limited faulting in response to thermal subsidence, one of the consequences being a westward thickening of the Lower Coal Measures across the Boothorpe Fault and Ashby Anticline.

The end-Carboniferous Variscan inversion event reactivated basement structures, reversing the throws of many Dinantian extensional faults (Figure 10). Inversion anticlines were formed within the Widmerpool Half-graben and deformation was intense along the north-west-oriented structures. A strongly asymmetrical syncline developed on the downthrown (south-western) side of the Thringstone (reverse) Fault, against which the Coal Measures were locally rotated to the vertical. The concealed Breedon Fault may have had a similar style of reverse movement judging by the near-vertical to locally overturned attitudes of Dinantian strata in the adjacent Breedon Hill, Cloud Hill and Barrow Hill quarries (Plate 3). Other major coalfield inversion structures include the Ashby Anticline flanked to the west by the Boothorpe Fault. Complex north-west-trending faults and tight, periclinal fold structures in the Coal Measures mark a zone of compression along the Coton Park Fault.

Syn-Triassic tectonism, mainly Scythian and Anisian in age, was associated with subsidence within the Needwood Basin. It is shown by monoclinal (down-west) flexuring in conjunction with reactivation of the Coton Park and associated faults, causing westward thickening of the Sherwood Sandstone Group, and by movement along the Boothorpe Fault which caused a local angular unconformity between the Moira and Polesworth formations. Post-Jurassic deformation is demonstrated by a displacement of about 95 m of the Lias Group along the Normanton Hills Fault; gentle synclinal warping is indicated by dips of the Triassic strata east of the Thringstone Fault (Figure 2). Palaeogene to Quaternary uplift is principally manifested by the flights of Anglian to Flandrian-age river terraces developed along the major drainage systems. They are in part attributed to drainage renewal within a regime of regional uplift that can be traced at least as far back as the early Neogene.

It should be noted that faults in this district are of ancient origin and are currently inactive. However, in common with other parts of Britain this district has been affected historically by earthquakes. Of particular note was the Derby earthquake of 11 February 1957, with an epicentre approximately located just to the north of Diseworth [SK 450 250]. With a magnitude of 5.3 ML (Local Magnitude), and a degree of disturbance corresponding to a maximum intensity of 6 to 7 EMS (European Macro-seismic Scale), this was one of the largest events to affect the UK landmass. It caused widespread damage to chimneys and roofs in the Derby–Nottingham–Loughborough areas, and to the Blackbrook Reservoir, about 7 km farther south. A magnitude 4.2 ML aftershock, maximum intensity 5 EMS, occurred the following day causing further damage to already weakened structures.

Chapter 3 Applied geology

Geological factors have played a significant role in the industrial expansion of Loughborough, Derby and Burton, and the urban conurbations of the coalfields. The legacy of deep mining, quarrying and heavy industrial development is areas of derelict and otherwise despoiled land. By considering the interplay between geological and manmade factors for a site at an early stage in the planning process, appropriate mitigation measures can be taken prior to development. Geological information may also be used to identify opportunities for development, particularly in respect of leisure, recreation and protection of sites of nature conservation interest.

Mineral resources

The economics of underground mining are unlikely to be favourable in the near future, so that potential mineral resources are those which can be won at or near to the surface. The main factors hindering extraction are significant thicknesses of overburden, including natural drift deposits and man-made deposits, sterilisation of resources by urban development and conflicts with other forms of land-use, with possible detrimental effects on the landscape. The main historically important mineral resources in the district are described in (Figure 11); the district also contains many notable base metal mineral occurrences of a smaller size, which have been reviewed by King (1968).

Surface mineral workings

Quarries or pits that remain open represent an important resource as they may provide a suitable repository for waste disposal, may be reopened for further mineral extraction or, as in the case of Morley Quarry [SK 4765 1787], may be developed as sites of educational, recreational and wildlife value. However, they can also be a constraint to development as steep rock faces may be unstable. Quarries and pits occur widely in this district mostly for hard-rock aggregate, coal or fireclay.

Engineering ground conditions

The key parameters relevant to construction and development are the suitability of the ground to support structural foundations, the ease of its excavation and its worth in engineered earthworks and fills. Some of these issues are summarised for the main engineering geological units in the district in (Figure 12). Foundation conditions are not only affected by the engineering properties of the substrate, but also by factors such as geological structure, slope stability, the presence of undermining and degree of weathering. The seismic history of this district is also relevant, as it has shown the potential for large-magnitude earthquakes to occur (see p.24). Variable man-made conditions, notably in landfill sites and areas of colliery spoil, are a potential problem with respect to severe differential settlement. Colliery spoil may contain iron pyrites that is prone to oxidise and produce sulphate-rich, acidic leachates, which could be harmful to concrete present in foundations or buried services, thus requiring the use of sulphate-resisting cement. This oxidation process may also result in expansion and differential heaving of foundations constructed on such deposits. Large volumes of quarry spoil, both ancient and modern, are common in this district, and the areas affected may present poor foundation conditions if large cavities are present, or if deposited on steep slopes. Sulphates occurring naturally in Triassic strata, particularly the Mercia Mudstone Group, may also have deleterious effects on concrete. Mudrocks, in particular the Coal Measures seatearths and parts of the Mercia Mudstone, may weather to show increases in natural moisture content, plasticity and swelling potential.

Subsidence risk due to undermining may be a potential constraint in areas of former underground mining of coal, fireclay, lead and gypsum. Coal and fireclay mining was particularly important in the south and west of the district (Figure 4), (Figure 5). In such areas, the principal concerns relate to ground instability caused by the collapse of unsupported shallow workings, such as bell pits and areas of pillar and stall workings. Structures straddling a fault may be susceptible to uneven settlement in areas prone to mining subsidence. Collapse of shaft fill, linings or cappings may also result in surface subsidence. Arup Geotechnics (1992) provided a review of mining subsidence in the UK. Information on recorded shafts and abandoned mines are lodged with the Coal Authority, who should be consulted prior to development in a coalfield area. Additional information on the distribution of ancient near-surface workings, including hitherto unrecorded shafts, that could be located in the field or on aerial photographs, is given on the relevant 1:10 000 scale geological maps. Gypsum mining was largely limited to workings in the Tutbury seam. These activities involved the driving of shafts and adits, and the abandoned mines of the Chellaston area are at shallow depths. The main concerns relate to ground instability including uneven settlement caused by voids or foundered workings, exacerbated by natural gypsum dissolution continuing within the abandoned workings. Information on the Aston and Chellaston area is provided by Cooper (1996, and references therein). Records of underground mining activities south-east of Thrumpton are lodged with British Gypsum PLC.

Mine-drainage waters may be a problem in areas of disused collieries, such as those prevalent in the south and south-west of the district. Such waters have high acidity, in addition to iron precipitation and commonly elevated levels of manganese, aluminium and sulphates, and where they reach the surface they can devastate flora and fauna.

Bedrock dissolution due to groundwater circulation is a potential risk in outcrops of the Cropwell Bishop Formation, which contain the major gypsum deposits of the district. The zone of solution may contain cavities, and may extend down to 30 m below the surface. In the Dinantian outcrops, the possibility that carbonate dissolution has formed near-surface voids cannot be entirely discounted, particularly as large caves have been encountered in some of the quarries.

Slope stability is an issue particularly where building development has extended on to steep valley sides. The majority of landslip features may be considered currently inactive. However, renewed instability may occur if the slope is adversely disturbed by undercutting or loading, or if increased volumes of water are introduced, such as may occur during development.

Pollution potential

Artificial (man-made) deposits may contain toxic residues, either as a primary component or generated secondarily by chemical or biological reactions, and are thus potential sources of pollution. Significant sites of potential pollution include areas of landfill and former gasworks, chemical works, textile mills, iron and steel works, railway sidings and sewage works. Leachate migration may be a problem where groundwater percolates through waste and becomes enriched in potentially harmful soluble components. The resultant leachate may migrate laterally in permeable superficial deposits or bedrock adjacent to the site, according to the depth of the unsaturated zone. This is potentially a most serious hazard at landfill sites situated on deposits in hydraulic continuity either with the Sherwood Sandstone, Dinantian or Millstone Grit aquifers or with river terrace deposits and alluvium. It may also apply to sites within highly faulted and jointed Precambrian rocks or on Coal Measures strata which may contain permeable sandstones.

Gas emissions

Gas emissions may represent a hazard in areas associated with the accumulation of the 'greenhouse gases' (methane and carbon dioxide) and carbon monoxide. These gases can be generated naturally in Coal Measures strata, or by the decomposition of materials in landfill sites. They sometimes migrate considerable distances through permeable strata and accumulate in poorly ventilated enclosed spaces such as basements, foundations or excavations. Methane is potentially explosive, may act as an asphyxiant and may cause vegetation die back. Carbon dioxide is toxic in high concentrations, may act as an asphyxiant, and may also cause vegetation die back; its escape at surface and underground has been reported from near Swadlincote. Carbon monoxide is potentially explosive and is toxic at low concentrations. Radon gas is commonly generated from minerals in Carboniferous limestones, such as those outcropping around Breedon.

Water resources

Reservoirs in upland areas to the north of the district provide the principal source of domestic water supply for Loughborough and Derby. Springs most commonly discharge on to slopes where groundwater flow in sandstone or limestone aquifers is interrupted by impermeable mudstones. They occur in certain parts of this district, and have historically provided local supplies of potable water. Groundwater provides public water supplies for some small villages and isolated farms and licensed water abstraction for industrial purposes occurs throughout the district. The major bedrock aquifers are the Sherwood Sandstone and Millstone Grit groups. Yields from both boreholes and springs in the Millstone Grit vary seasonally and are known to dry up in summer; however, the quality of the water is better than that from the Coal Measures. The Mercia Mudstone Group generally acts as an aquiclude, but thin sandstones within the mudstone may yield small local supplies; overall similar volumes are abstracted as from the whole of the Carboniferous. Sands and gravels within the alluvium and terrace deposits of the River Trent form a major aquifer in this district. Such shallow aquifers are in hydraulic continuity with the river waters and thus both are vulnerable to pollution.

Flooding is a potential problem in the district. For example, after the serious floods in 1947 a programme of flood protection works was initiated. Peak flows recorded since then did not result in serious flooding of built-up areas until the major floods of early November 2000. Information about flood-risk limits can be provided by the Environment Agency at West Bridgford, Nottingham. Sheet 141 Loughborough shows that the major river floodplains contain large tracts of river terrace deposits, which are slightly higher than the surrounding alluvium and consequently outline areas of generally lower flood frequency. The distribution of these deposits, and of the alluvium, should therefore form the basis for any plan to manage flood risk.

Conservation sites

Several sites have been identified in the district as important to earth science research and teaching and for recreational purposes. Some of these are in disused quarries and pits. The upper level at the north-eastern end of Newhurst Quarry [SK 488 179] has been designated as a Site of Special Scientific Interest (SSSI) on account of the occurrence of the rare vanadium mineral, vesigniéite. Morley Quarry [SK 4765 1787], exposing Precambrian rocks and the sub-Triassic unconformity, is both a local conservation site and a Regionally Important Geological Site (RIGS).

Information sources

Further information held by the British Geological Survey relevant to the Loughborough district is listed below. Searches of indexes to these and many other data collections can be made on the Geosciences Index System in BGS libraries.

Other information, including a Geoscience Data Index, is avaliable on the BGS Website http://www.bgs.ac.uk.

Maps

The maps covering the 1:50 000 Series Sheet 141 Loughborough are listed below, together with surveyors' initials and dates of the survey. The surveyors were K Ambrose, A Brandon, W J Barclay, J N Carney, A H Cooper, D V Frost, A S Howard, R A Old, J G O Smart and B C Worssam. The maps are not published but are available for public reference in the libraries of the BGS in Keyworth and Edinburgh and the BGS London Information Office in the Natural History Museum, South Kensington, London. Uncoloured dyeline copies are available for purchase from BGS Sales Desk; some sheets are available coloured and in digital format (marked with *).

SK21NE JNC/BCW 1966/95 WA/96/11
SK22SE AB 1996 WA/96/77
SK23NE JGOS 1966
SK23SE AB/AHC 1995 WA/97/03
SK31NW JNC/BCW 1968/94 WA/96/11
SK31NE JNC/BCW/RAO 1968/95 WA/96/02
SK32NW AB 1996 WA/97/02
SK32NE KA 1995 WA/97/40
SK32SW WJB 1995 WA/96/78
SK32SE KA/JNC 1995 WA/97/17
SK33NW JGOS 1966
SK33NE JGOS 1965
SK33SW* AHC 1995 WA/97/64
SK33SE* AB 1995 WA/96/07
SK41NW JNC/RAO 1974/93 WA/94/08
SK41NE JNC/RAO 1974/93 WA/94/08
SK42NW KA 1996 WA/96/41
SK42NE AB/JNC 1996 WA/97/04
SK42SW AB 1994 WA/97/42
SK42SE JNC 1996 WA/96/100
SK43NW DVF 1964
SK43NE DVF 1964
SK43SW AB 1994 WA/96/07
SK43SE* AB 1994 WA/96/07
SK51NW JNC/RAO 1974/93 WA/94/08
SK52NW JNC/AHC 1996 WA/97/46
SK52SW* AB 1993 WA/94/60
SK53NW DVF 1964
SK53SW ASH 1987 WA/89/05

Books

Documentary collections

Basic geological survey information, which includes 1:10 000 or 1:10 560 scale field slips and accompanying field notebooks, are archived at the BGS.

Boreholes and shafts

Borehole and shaft data for the district are catalogued in the BGS archives at Keyworth. For further information contact: the Manager, National Geosciences Records Centre, BGS, Keyworth.

Mine plans

BGS maintains a partially complete collection of plans of underground mines for coal and other minerals, mostly for gypsum.

Geophysics

Gravity and aeromagnetic data are held digitally in the National Gravity Databank and the National Aeromagnetic Databank at BGS Keyworth. Seismic reflection data is available for the south-western and central to eastern parts of the district. The profiles are from surveys by Fina, Charterhouse, British Petroleum, Edin-burgh Oil and Gas and the National Coal Board (NCB). Geophysical logs are available for some boreholes, the principal ones being the Ratcliffe on Soar (SK52NW/72) and Long Eaton No. 1 (SK43SE/161) hydrocarbon boreholes and the BGS Melbourne (SK32SE/39), Ticknall (SK32SE/ 103), Worthington (SK42SW/204), Morley Quarry (SK41NE/30) and Hanging Hill Farm (SK31NW/141) boreholes.

Hydrogeology

Data on water boreholes, wells and springs and aquifer properties are held in the BGS database at Wallingford.

BGS Lexicon of named rock unit definitions

Definitions of the named rock units shown on BGS maps, including those shown on the 1:50 000 Series Loughborough Sheet 141 are held in the BGS Lexicon database, which can be accessed on the BGS web site.

Material collections

Palaeontological collection

Macrofossils and micropalaeontological samples collected from the district are held at BGS Keyworth.

Petrological collections

The petrological collections for the district consist of about 700 hand specimens and 500 thin sections. These are held in the England and Wales Sliced Rocks collection at BGS Keyworth.

Geochemical samples

A database of silicate and trace element analyses from the district is held at BGS.

Borehole core collection

Samples and entire core from a small number of boreholes in the Loughborough district are held by the National Geosciences Records Centre, BGS, Keyworth.

BGS photographs

Copies of these photographs are deposited for reference in the BGS library, Keyworth. Colour or black and white prints and transparencies can be supplied at a fixed tariff.

Other relevant collections

Mine abandonment plans

Coal abandonment plans are held by The Coal Authority, Mining Reports, 200 Lichfield Lane, Mansfield, Nottinghamshire, NG18 4RG. Gypsum mine plans are held by British Gypsum Plc., East Leake, Loughborough, Leicestershire, LE12 6JQ.

Groundwater licensed abstractions, catchment management plans and landfill sites

Information on licensed water abstraction sites, for groundwater, springs and reservoirs, Catchment Management Plans with surface water quality maps, details of aquifer protection policy and extent of washlands and licensed landfill sites are held by the Environment Agency.

Earth science conservation sites

Information on the Sites of Special Scientific Interest present within the Loughborough district is held by English Nature, Headquarters and Eastern Region, Northminster House, Peterborough, PE1 2UU.

References

Most of the references listed below are held in the Library of the British Geological Survey at Keyworth, Nottingham. Copies of the references can be purchased subject to the current copyright legislation.

ARUP GEOTECHNICS. 1991. Review of mining instability in Great Britain. Report to the Department of the Environment, Arup Geotechnics, Ove Arup and Partners. (London: HMSO.)

BLAND, B H, and GOLDRING, R. 1995. Teichichnus Seilacher 1955 and other trace fossils (Cambrian?) from the Charnian of Central England. Neues Jb. Palaeont. Abh, Vol. 195, 5–23.

BOYNTON, H E, and FORD, T D. 1995. Ediacaran fossils from the Precambrian (Charnian Supergroup) of Charnwood Forest, Leicestershire. Mercian Geologist, Vol. 13, 165–183.

BOYNTON, H E, and FORD, T D. 1996. Ediacaran fossils from the Precambrian of Charnwood Forest — corrigendum. Mercian Geologist, Vol. 14, 2–3.

BRANDON, A, and SUMBLER, M G. 1988. An Ipswichian fluvial deposit at Fulbeck, Lincolnshire and the chronology of the Trent terraces. Journal of Quaternary Science, Vol. 3, 127–133.

BRANDON, A, and SUMBLER, M G. 1991. The Balderton Sand and Gravel: pre-Ipswichian cold stage fluvial deposits near Lincoln, England. Journal of Quaternary Science, Vol. 6, 117–138.

CARNEY, J N. 1999. Revisiting the Charnian Supergroup: new advances in understanding old rocks. Geology Today, Vol. 15, 221–229.

CARNEY, J N. 2000. Igneous processes within late Precambrian volcanic centres near Whitwick, northwestern Charnwood Forest. Mercian Geologist, Vol. 15, 7–28.

CARNEY, J N, AMBROSE, K, and BRANDON, A. 2001. Geology of the country between Loughborough, Burton and Derby. Sheet Description of the British Geological Survey, Sheet 141 (England and Wales).

CLAYTON, K M. 1953. The glacial chronology of part of the Middle Trent Basin. Proceedings of the Geologists' Association, Vol. 64, 198–207.

COOPER, A H. 1996. Gypsum: geology, quarrying, mining and geological hazards in the Chellaston and Aston-on-Trent areas. 1:10 000 sheets SK33SE, SK32NE, SK43SW and SK42NW. British Geological Survey Technical Report, WA/96/30.

CORNWELL, J D, and ROYLES C P. 1998. Geophysical investigations in the Loughborough district. British Geological Survey Technical Report, WK/98/05.

EBDON, C C, FRASER, A J, HIGGINS, A C, MITCHENER, B C, and STRANK, AR E. 1990. The Dinantian stratigraphy of the East Midlands: a seismotectonic approach. Journal of the Geological Society of London, Vol. 147, 519–537.

FALCON, N L, and KENT, P E. 1960. Geological results of petroleum exploration in Britain, 1945–1957. Memoir of the Geological Society of London, Vol. 2.

FISHER, R V, and SCHMINCKE, H-U. 1984. Pyroclastic Rocks. (New York: Springer-Verlag.)

FORD, T D. 1979. The history of the study of the Precambrian rocks in Charnwood Forest, England. 65–80 in History of concepts in Precambrian geology, KUPSCH, WO and SARJEANT, WA S (editors). Special Paper of the Geological Association of Canada, No. 19. FOX-STRANGWAYS, C. 1905. The geology of the country between Derby, Burton-on-Trent, Ashby-de-la-Zouch and Loughborough. Memoir of the Geological Survey of Great Britain, Sheet 141 (England and Wales). FOX-STRANGWAYS, C. 1907. The geology of the Leicestershire and South Derbyshire Coalfields. Memoir of the Geological Survey of Great Britain (England and Wales).

FRASER, A J, and GAWTHORPE, R L. 1990. Tectono-stratigraphic development and hydrocarbon habitat of the Carboniferous in northern England. 49–86 in Tectonic Events Responsible for Britain's Oil and Gas Reserves. HARDMAN, RF P, and BROOKS, J. (editors). Special Publication of the Geological Society, No. 55

FULTON, I M, and WILLIAMS, H. 1988. Palaeogeographical change and controls on Namurian, Westphalian A and Westphalian B sedimentation at the southern margin of the Pennine Basin. 148–199 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of Northwest Europe. BESLY, B M, and KELLING, G. (editors). (Glasgow and London: Blackie.)

GRADSTEIN, F M, and OGG, J. 1996. A Phanerozoic time scale. Episodes, Vol. 19, 3–5.

HALLSWORTH, C. 1998. Stratigraphic variations in the Millstone Grit in the Melbourne area: implications for provenance. British Geological Survey Technical Report, WA/98/53e.

HOBBS, PR N. 1998. Engineering geological assessment of Loughborough 1:50 000 Sheet 141. British Geological Survey Technical Report, WN/98/7.

JONES, N S. 1994. Sedimentology of Westphalian A and B strata from the Leicestershire and South Derbyshire Coalfields. British Geological Survey Technical Report, WH/94/286R.

KING, R J. 1968. Mineralization. 112–137 in The Geology of the East Midlands. SYLVESTERBRADLEY, PC, and FORD, T D. (editors). (Leicester University Press)

KNOX, RW O'B. 1996. Heavy mineral analysis of borehole sections in the Sherwood Sandstone Group of the Loughborough Sheet. British Geological Survey Technical Report, WH/96/69R. LEE, M K, PHARAOH, T C, and SOPER, N J. 1990. Structural trends in central Britain from images of gravity and aeromagnetic fields. Journal of the Geological Society of London, Vol. 147, 241–258.

LEWIS, M A. 1998. The hydrogeology of the Loughborough district. British Geological Survey Technical Report, WD/98/28.

MCILROY, D, BRASIER, M D, and MOSELEY, J M. 1998. The Proterozoic-Cambrian transition within the 'Charnian Supergroup' of central England and the antiquity of the Ediacara fauna. Journal of the Geological Society of London,Vol. 155, 401–413.

MITCHELL, G H, and STUBBLEFIELD, C J. 1941. The Carboniferous Limestone of Breedon on the Hill, Cloud, Leicestershire, and the associated inliers. Geological Magazine, Vol. 78, 201–219.

MOLYNEUX, S G. 1995. Palynology of the basement beds, BGSTicknall Borehole No.1: 182.75–208.82 m. British Geological Survey Technical Report, WH/95/244R.

MOSELEY, J, and FORD, T D. 1985. A stratigraphic revision of the Late Precambrian rocks of the Charnwood Forest, Leicestershire. Mercian Geologist, Vol. 10, No.1, 1–18.

NOBLE, S R, TUCKER, R D, and PHARAOH, T C. 1993. Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U–Pb and Nd isotopes. Geological Magazine, Vol. 130, 835–846.

PHARAOH, T C, and EVANS, C J. 1987. Morley Quarry No.1 Borehole: geological well completion report. Investigation of the Geothermal Potential of the U K, British Geological Survey Report.

PHARAOH, T C, WEBB, P C, THORPE, R S, and BECKINSALE, R D. 1987. Geochemical evidence for the tectonic setting of late Proterozoic volcanic suites in central England. 541–552 in Geochemistry and mineralization of Proterozoic volcanic suites. PHARAOH, T C, BECKINSALE, R D, and RICKARD, D (editors). Special Publication of the Geological Society of London, No. 33.

POSNANSKY, M. 1960. The Pleistocene succession in the middle Trent basin. Proceedings of the Geologists' Association, Vol. 71, 285–311.

RICE, R J. 1968. The Quaternary deposits of central Leicestershire. Philosophical Transactions of the Royal Society of London, Series A, Vol. 262, 459–509.

RUSHTON, AW A. 1995. The basement beds in the Ticknall Borehole, Derbyshire. British Geological Survey Technical Report, WH/95/227R.

TUCKER, R D, and PHARAOH, T C. 1991. U-Pb zircon ages for Late Precambrian igneous rocks in southern Britain. Journal of the Geological Society of London, Vol. 148, 435–443.

WATTS, W W. 1947. Geology of the ancient rocks of Charnwood Forest, Leicestershire. (Leicester: Leicester Literary and Philosophical Society.)

WORSSAM, B C, and OLD, R A. 1988. Geology of the country around Coalville. Memoir of the British Geological Survey, Sheet 155 (England and Wales).

Index to the 1:50 000 Series maps of the British Geological Survey

The map below shows the sheet boundaries and numbers of the 1:50 000 Series geological maps. The maps are numbered in three sequences, covering England and Wales, Northern Ireland, and Scotland.The west and east halves of most Scottish 1:50 000 maps are published separately. Almost all BGS maps are available flat or folded and cased.

(Index map)

The area described in this sheet explanation is indicated by a solid block.

British geological maps can be obtained from sales desks in the Survey's principal offices, through the BGS London Information Office at the Natural History Museum Earth Galleries, and from BGS-approved stockists and agents.

Figures and plates

Figures

(Figure 1) Summary of the geological succession in the district.

(Figure 2) Geology of the Loughborough district.

(Figure 3) Distribution of the Precambrian and Lower Cambrian rocks of the northern Charnwood Forest.

(Figure 4) Coal seams of the North-west Leicestershire Coalfield.

(Figure 5) Coal seams and fireclays (in italics) of the South Derbyshire Coalfield.

(Figure 6) Lithostratigraphy of the Sherwood Sandstone and Mercia Mudstone groups, showing their 'signatures' produced by borehole gamma-ray (GR) and sonic (SON) logs.

(Figure 7) Correlation of Quaternary glacigenic and fluvial deposits (modified from Brandon and Sumbler, 1991).

(Figure 8) Quaternary deposits.

(Figure 9) Palaeochannels infilled with glacigenic sediments in the Trent valley downstream of Burton on Trent and in the Derwent valley downstream of Derby.

(Figure 10) Main structures and sub-Mesozoic geology of the district.

(Figure 11) Principal mineral resources of historic importance in the district.

(Figure 12) Geotechnical data for the main geological units in the district.

Plates

(Plate 1) Tuffaceous sandstone turbidite bed at Ives Head Formation [SK 4769 1704]. It shows normal grading, from a structureless coarse-grained base to a parallel-stratified middle section (above hammer head) and into a finely laminated muddy and silty top (GS 1071).

(Plate 2) Exposure of the Cademan Volcanic Breccia in Grace Dieu Wood [SK 4353 1746], showing highly angular andesite blocks, the margins of which locally have a 'jig-saw' fit (GS 1004).

(Plate 3) Well-bedded dolostones of the Milldale Limestone Formation tilted to the vertical on the eastern face of Breedon Hill Quarry [SK 407 233] (GS 1072).

(Plate 4) Concertina folding of bedded dolostones in the Cloud Wood Member, basal to the Cloud Hill Dolostone Formation, northern part of the Cloud Hill Quarry (GS 1070). [SK 412 218]

(Plate 5) Strata of the Middle Coal Measures, 'Pottery Clays Formation' in the north-east face of the Donington Extension opencast site [SK 3064 1765]. The pale grey sandstone represents a section through the laterally-accreting bar deposit of a former river channel. The exposed shaft is probably of pre-19th century construction, with metal hoops and wooden supporting struts (GS 1014).

(Front cover) Cover Photograph: Dinantian rocks of the Milldale Limestone Formation exposed in the face of Breedon Hill Quarry, viewed from the east [SK 411 232]. The main pit of the quarry is below the viewing level. Breedon Hill formed a major element of the Permo–Triassic topography, before being buried by mid-Triassic strata of the Mercia Mudstone Group. The latter's outcrop gives rise to red, clay-rich soils typified by the ploughed fields in the foreground (MN 32052). Photo by C F Adkin.

(Rear cover)

(Index map) Index to the 1:50 000 Series maps of the British Geological Survey

Figures

Figure 4 Coal seams of the North-west Leicestershire Coalfield

Coal seam (alternative name) Map code Thickness (m) Former extent of workings
Minge Coal (Stone Smut Rider, Forest) MI 0.9–1.6 Initial workings at outcrop or near-surface (bell pits, pillar and stall); produced extensive disturbed ground, as seen at Peggs Green [SK 4150 1770] and woods near Lount [SK 397 190]. Subsequently worked out underground from numerous (undocumented) shafts and modern collieries, all now closed. Recently worked at surface from large opencast sites, such as that near Lount [SK 385 186], which are now mostly restored
Five Feet Coal (Block, Stone Smut) FF 0.6–2.2
Splent Coal (Swannington) SP 0.6–1.6
Threequarters Coal (Jack Head, Two Foot, Soft) TQ 0.6–0.7
New Main Rider Coal (Slate Rider) NMR 0.2–0.7
New Main Coal (Slate, Swannington Main, Ten Foot Mine) NMA 1.4–2.0
Swannington Yard Coal (Yard) SY 0.7–1.5
High Main Coal (Stinking, Stinking Rider) HM 0.9–2.0
Upper Main Coal (Main, Main-Lower Leaf) UM 1.2–2.3
Smoile Coal (Ell) SM 0.7–1.3
Upper Lount Coal (Second Lount, Yard) UL 0.2–1.4
Middle Lount Coal ML 1.4–2.0 Mine, surface workings (including for fireclay), bell pits
Nether Lount Coal NL 0.8–1.8 Mine, surface workings, bell pits
Yard Coal YC 0.6–1.0 Mine, surface workings
Lower Main (Upper Leaf) LMU 0.1–1.2 Mine, ?surface workings, bell pits
Lower Main (Lower Leaf) (Roaster, Deep Main) LML 0.1–0.8 Mine and surface workings
Clod Coal CL 0.1–0.6 Mine, surface workings, bell pits
Kilburn Coal K 0.2–3.8 Mine, surface workings, bell pits; ironstone mined from beds above
Alton Coal AL 0.5 Not worked

Figure 5 Coal seams and fireclays (in italics) of the South Derbyshire Coalfield

Coal seam (alternative name) Map code Thickness (m) Former extent of workings
P30–P12 0.1–2.0 (Range) 'Pottery Clays Formation': formerly mined underground for coal and fireclay. Presently worked opencast from sites such as Donnington Extension [SK 305 173] where clay stockpiled; coal mainly a by-product. Sites now in various stages of expansion or restoration
P31 (Derby) 0.1–1.0
Marl 1.0
Crucible, Main & Derby fireclays 1.0–3.0
Bottle Clay 1.2–3.7
P32 Rider
Seatearth (no name) 0–1.8
P32/33 c. 1.0
Deep Fireclay, White Clay, 1.5–4.0
Deep Clunch, Brown Clay
P33/34 (Ell) 0.3–1.7
P40–P35 0.3–1.5 (Range) for all seams)
Upper Kilburn (Dicky Gobler) UK 0.1–1.4 Mine workings
Block Coal (Stone Smut, Jack Dennis, Watson) B 0.1–1.7 Mine, surface workings
Yard Coal Y 0.1–1.4 Mine, surface workings
Upper Cannel Coal UC 0.3–1.0 Mine, surface workings
Little Coal (Five feet, Four Foot) L 0.1–1.9 Mine, surface workings
Little Kilburn Coal (Smith’s, Smuts, Cannel) LK 0–2.0 Mine, surface workings
Main coals:
Rider
Over OM 3.4–6.0 Mine, surface workings
Nether (Little Woodfield Rider) NM
Little Woodfield Coal LW 0.6–2.4 Mine, surface workings
Lower Main Coal (Shale, Slate) LM 0–1.2 Mine, surface workings
Woodfield Coal WD 1.4–12.8 Mine, surface workings; local fireclay resource
Stockings Coal (Two Yard, Low Main, Linton) ST 1.4–2.6 Mine, surface workings, ?bell pits
Eureka Coal (Bottom) E 0.3–1.6 Mine workings ?bell pits
Joice’s Coal (Joicey) J 0.1–0.9 Mine workings
Stanhope Coal SH 0.3–1.5 Mine, surface workings
Well Coal (Threequarter) W 0.1–1.6 Mine workings
Twelve Inch Coal TI 0–0.6 Not worked
Clod Coal CL 0–0.5 Mine, surface workings,
Kilburn Coal K 0.7–1.7 bell pits
Norton Coal N 0–0.8 Not worked
Alton Coal AL 0–1.2 Not worked

Figure 7 Correlation of Quaternary glacigenic and fluvial deposits (modified from Brandon and Sumbler, 1991)

Stage Approximate age of commencement in years BP o.i. stage Lower Derwent Lower Soar (Rice, 1968) Trent (above Nottingham) and Lower Dove
Flandrian 1 Alluvium Alluvium Alluvium Warm temperate
10 000 Hemington Terrace Deposits Hemington Terrac eDeposits * Warm temperate
Devensian 26 000 2 Syston Sand and Gravel * Holme Pierrepont Sand and Gravel * Cold (glacial)
65 000 3
80 000 4 Allenton Sand and Gravel Wanlip Sand and Gravel Beeston Sand and Gravel Cold (periglacial)
115 000 5d-a
Ipswichian 128 000 5e Crown Inn Beds * Warm temperate
‘Wolstonian’ 195 000 6 Borrowash Sand and Gravel Birstall Sand and Gravel Egginton Common Sand and Gravel Cold (periglacial)
‘Ilfordian’ 240 000 7 Warm temperate
‘Wolstonian’ 297 000 8 Ockbrook Sand and Gravel Knighton Sand and Gravel ** Etwall Sand and Gravel Cold (periglacial)
Hoxnian 330 000 9 Warm temperate
Anglian 367 000 10 Eagle Moor Sand and Gravel (in part?) Eagle Moor Sand and Gravel (in part) Cold (periglacial)
‘Swanscomian’ 400 000 11 Warm temperate
Anglian 12 Eagle Moor Sand and Gravel Eagle Moor Sand and Gravel Cold (glacial)
Findern Clay Cold (glacial)
Oadby Till Oadby Till Oadby Till Cold (glacial)
500 000 Thrussington Till Thrussington Till Thrussington Till Cold (glacial)
* Signifies that the terrace deposit is ascribed to an oxygen isotope (o.i) stage on the basis of biostratigraphy, absolute age determination, detailed stratigraphy and sedimentology or presence of palaeosol

Dark blue cold (glacial); Pale blue cold (periglacial); Pink Warm temperate (2020 note: Column added to denote this)

Figure 8 Quaternary deposits

Deposit Morphology and thickness (m) Description
Till (boulder clay) wide featureless spreads, or narrow elongate outcrops where confined to palaeochannels. Oadby Till: lodgement till of over-consolidated brown to blue-grey clay, red in Triassic-rich variant; scattered pebbles and fragments of flint, chalk. Jurassic limestone and various Jurassic fossils common
Generally less than 5; up to 20 recorded in palaeochannels Thrussington Till: lodgement till of over-consolidated red to red-brown clay, silty or sandy. Rock fragments of green-grey Triassic siltstone or sandstone and quartz/quartzite pebbles. Common Carboniferous sandstone and limestone fragments
Glaciofluvial variable; up to 12 in palaeo-channels brown or grey, bedded, unconsolidated to loosely cemented sands, gravels or silts; clasts are of ‘Oadby’ or ‘Thrussington’ derivation
Glaciolacustrine thin, impersistent; up to 19 in Elvaston Palaeochannel grey to brown, over-consolidated clay or silt, local rock fragments (dropstones) and carbonate nodules (‘race’). Variably laminated to blocky. In palaeochannels the ‘Findern Clay’ has sand lenses
Head (solifluction) and/or colluvial deposits) found in hollows, at bases of slopes or on river terraces; variable, 0–10 poorly consolidated and unsorted deposit, composition reflects that of upslope source material; may contain shear surfaces
River terrace wide, flat-topped terraces, small mounds (‘eyots’) or restricted spreads; up to 12 grey or brown, bedded, unconsolidated silt, sand and gravel, locally with lenses of silty clay or organic-rich ‘peaty’ clay. Clast types reflect source region, e.g. Carboniferous limestones are common in Derwent terrace deposits
Alluvium narrow outcrops; widespread flats along trunk streams; up to 5 heterogeneous silt and sand with gravel lenses; organic-rich clay and peat in former meanders
Lacustrine as wide flats occupying shallow depressions; up to 3 dark grey stiff to plastic clay or silty clay, commonly with nodular carbonate ‘race’. May contain shell-rich layers, and beds of organic-rich clay or peat. Common basal thin sand or gravel
Landslip hummocky, terraced or lobate features; variable thickness slipped masses of bedrock or drift; rotational failures and debris flows are common

Figure 11 Principal mineral resources of historic importance in the district

Mineral resource Source (main source) in bold) Activity Use
Sandstone Millstone Grit, Bromsgrove Sandstone, Wingfield Flags former quarries; no current activity walls, paving, cladding; local use for sand
‘Hard rock’ Precambrian and Dinantian rocks currently worked from large quarries; many small disused workings road aggregate, ornamental gravel, walling and cladding
Sand and gravel River Trent terrace deposits, glaciofluvial deposits currently worked; numerous former workings concrete aggregate, building and asphalt sand
‘Limestone’ Dinantian rocks, Jurassic (Barnstone Member) numerous small to medium size quarries; no current use building stone or flux for local smelting industries
Coal Coal Measures formerly mined and opencasted; currently opencasted in South Derbyshire Coalfield engine and household use; generally noncaking coals, commonly high in sulphur
Fireclay Middle and Upper Coal Measures (mainly above P40 Coal); Lower Coal Measures formerly mined and opencasted in South Derbyshire Coalfield; currently opencasted facing bricks, vitrified clay pipes, refractory products; formerly for pottery, pipework
Brickclay Mercia Mudstone numerous quarries and small pits. Currently quarried near Shepshed [SK 4792 1796] building bricks, agricultural clay
Ironstone Mudstones above Kilburn Coal mined from bell pits; no current activity iron smelting
Galena, blende Small lodes at Dinantian/ Namurian junction; local enrichments in Triassic sandstones and at base-Triassic unconformity mined near Staunton Harold and Tickow Lane bridge [SK 4269 1864]; no current activity lead, zinc
Gypsum Tutbury seam of the Cropwell Bishop Formation former shallow workings near Aston on Trent. Recently mined SE of Thrumpton; no current activity plasterboard, insulation, dry-lining and decorative materials

Figure 12 Geotechnical data for the main geological units in the district

ENGINEERING GEOLOGICAL UNITS GEOLOGICAL UNITS CHARACTERISTICS FOUNDATIONS
SOILS
MIXED Loose/dense Till (boulder clay) Stiff/v.stiff stony sandy CLAY/variable Generally good but depends on water bearing sand/silt layers/lenses
COHESIVE/ NON-COHESIVE SOILS Soft/firm Seatearth, Head Soft-firm CLAY, sandy Silty CLAY. Highly variable (head) Generally poor due to high variability, presence of relict shears & plasticity
Alluvium, Lacustrine alluvium Glaciolacustrine deposits Soft-firm, loose-dense, fine-coarse, CLAY, SILT, SAND, GRAVEL Soft, highly compressible (organic?) zones. Dense gravels are good
NON-COHESIVE SOILS Med Dense River terrace deposits Glaciofluvial deposits Medium dense SAND & GRAVEL with laminated silts Generally good. Variable thickness in channels
MAN MADE DEPOSITS Made Ground Infilled Ground Highly variable in composition, depth, & density Very variable. May be very compressible. Pollution hazard
LANDSLIDE DEPOSITS Landslide Variable. Content as per origin but weaker; voided, saturated? Generally unsuitable unless special measures taken to stabilise ground
ROCK
WEAK SANDSTONE Mercia Mudstone Group (Parts) Very weak to strong, thinly bedded, flaggy SANDSTONE, SAND Generally good depending on thickness, cementation, & weathering state
STRONG SANDSTONE Coal Measures Millstone Grit (Parts) Strong to extremely strong, thickly bedded, blocky SANDSTONE Good foundation. Presence of open joints, block movement possible on slopes?
MUDROCKS Soft/hard Penarth Group, Lias Group Mercia Mudstone (Parts) Coal Measures (Parts) Soft MUDROCK - hard CLAY. Fissured, jointed, shaly? Plasticity generally low but locally high Generally good, but variable. If high plasticity, subject to heave. Slaking on exposure. Sulphate attack on concrete
LIMESTONES Carboniferous 1st. Barnstone M. 1st. Penarth Group Strong to extremely strong LIMESTONE & muddy limestone Generally good if nonvoided, non-karstic. Mining subsidence hazard
VERY STRONG VOLCANIC & METAMORPHIC ROCKS Charnian Supergroup Strong to extremely strong bedded volcaniclastics. Highly jointed & faulted Generally good. Removal of loose/weathered material may be required